A wind turbine generator (hereinafter also referred to as “wind turbine”) is an apparatus that generates electric power with a generator that is driven in such a manner that a rotor head equipped with wind turbine blades rotates when receiving wind power and increases the rotational speed using a gearbox.
The rotor head described above is attached to an end of a rotatable nacelle that is mounted on a wind turbine tower (hereinafter referred to as “tower”) and is supported so as to be rotatable about a substantially horizontal lateral rotation axis.
The nacelle of the wind turbine generator accommodates, as a general device configuration, a transmission unit for mechanical rotational power received from the wind turbine blades and a power generation unit. Between these, the rotational-power transmission unit is equipped with a main shaft bearing and a gearbox, and the power generation unit is equipped with a generator, a transformer, an inverter, and a control panel, or a generator and a control panel.
In such devices inside the nacelle, for the main shaft bearing and the gearbox that constitute the mechanical transmission unit, lubricating of the rotating portions and cooling of frictional heat are performed using lubricating oil circulating in a lubricating-oil circulation system 10, as shown in FIG. 6, for example.
In FIG. 6, reference sign 1 denotes a wind turbine generator, 2 denotes a tower, 3 denotes a nacelle, 4 denotes a rotor head, 5 denotes a wind turbine blade, 6 denotes an air intake portion, 7 denotes an exhaust portion, 8 denotes a main shaft bearing, 9 denotes a gearbox, and arrow Ah indicates heat radiation.
The lubricating-oil circulation system 10 described above is equipped with an oil tank 11 that stores lubricating oil, an oil pump 12 that circulates the lubricating oil, and an oil cooler 13 that cools the lubricating oil by exchanging heat with the outside air and connects these devices with a lubricating oil pipe 14 to form a closed-circuit lubricating oil circulation passage in the nacelle 3. The oil tank 11 is provided, for example, in the gearbox 9.
In the drawing, reference sign 13a denotes an oil cooler fan, 15 denotes a bypass pipe that forms a lubricating oil passage that bypasses the oil cooler 13, 16 denotes a bypass valve that is provided in the bypass pipe and opens in a state in which the lubricating oil temperature is lower than a predetermined value, 17 denotes an oil filter provided downstream of the oil pump 12, and 18 denotes an oil heater that heats the lubricating oil in the oil tank 11.
That is, the bypass valve 16 is a valve that opens when the lubricating oil increases in viscosity at a low temperature to cause a large pressure loss exceeding a predetermined value when it passes through the oil cooler to open the bypass pipe 15, and the oil heater 18 is used when the wind turbine generator 1 is started under the condition that the lubricating oil temperature is lower than a predetermined temperature, such as when the outside air is in a cold state. A heat exchanger using plate fins is often used as the oil cooler 13.
The outside air that exchanges heat with the lubricating oil in the oil cooler 13 described above is taken in through the air intake portion 6 provided at the lower portion of the front end face of the nacelle 3, as indicated by arrow Ao in the drawing, by operation of the oil cooler fan 13a. The outside air flows inside the nacelle 3 to ventilate it, passes through the oil cooler 13 to absorb heat from the lubricating oil, and is finally discharged outside through the exhaust portion 7 that opens at the top of the nacelle 3.
The air intake portion 6 that introduces the outside air is provided with a louver 6a and a salt-proof, dust-proof filter 6b, as shown in FIG. 7, for example.
Of the devices installed in the nacelle 3, examples of the other heat sources include a transformer 21, an inverter 22, a control panel (not shown), and a generator 23 connected to the rotor head 4, as shown in FIGS. 8 and 9, for example.
The inverter 22 is often equipped with a cooling system 30 that uses cooling water because an internal electric device 22a generates a lot of heat.
The inverter cooling system 30 is constituted by an endothermic heat exchanger 31 that cools the internal electric device 22a, a cooling-water pump 32, a cooling-water filter 33, a cooling-water tank 34, and a radiative heat exchanger 35, as shown in FIG. 8, for example, and constitutes a closed-circuit cooling water circulation system connected by a refrigerant pipe 36. However, the inverter 22 is sometimes installed outside the nacelle 3, for example, at the lower portion of the tower 2. Reference sign 35a in the drawing denotes the fan of the radiative heat exchanger 35.
The transformer 21 is often cooled such that the outer surface of a coil 21a is cooled by air because of its electrical insulation. The outside air or nacelle air is used as the air. However, the transformer 21 is sometimes installed outside the nacelle 3, for example, at the lower portion of the tower 2, like the inverter 22.
A cooling system 40 for the generator 23 is constituted by a closed primary-system cooling system 40A including the winding of the generator 23 and a secondary-system cooling system 40B. Reference sign 23a in the drawing denotes the rotor of the generator 23, and 23b denotes the stator.
The primary-system cooling system 40A often uses air as a cooling medium because of its electrical insulation. The primary-system cooling system 40A shown in FIG. 9 forms a primary airflow indicated by arrow A1 by operating a primary-system air fan 41.
On the other hand, the secondary-system cooling system 40B is equipped with a heat exchanger 42 that exchanges heat between the nacelle air and the primary-system air. In the heat exchanger 42 in this case, the primary-system air circulates to absorb heat from the generator 23, and the primary-system air that has increased in temperature radiates heat into the nacelle air. Reference sign 43 in the drawing denotes a secondary air fan, which takes in the nacelle air or the like and supplies it to the heat exchanger 42, and the secondary-system air that has exchanged heat with the primary system air passes through an exhaust passage 44 and is discharged outside the nacelle 3 through an exhaust port 44a. 
Alternatively, an intermediate medium, such as cooling water, is sometimes used to constitute the cooling system.
Patent Literatures 1 and 2 below disclose taking the outside air in and out independently from the nacelle air to/from a generator heat exchanger disposed in or at the upper part of the nacelle. In this case, a fluid in a primary system that constitutes a closed system is air, which differs from the present patent.